Thermoelectric (TE) energy conversion is a solid state technology which converts electrical energy into thermal energy or vice-versa. Thermoelectric energy is sometimes seen as a cleaner form of energy which reduces greenhouse gas emissions as compared to conventional energy generation. This technology has been used in cooling, refrigeration, and power generation. Thermoelectric energy has potential applications in waste heat recovery, for instance in automotive exhaust systems. The efficiency of this thermoelectric conversion is determined by the dimensionless property of the material called a figure of merit (ZT) which depends on the Seebeck coefficient (S), electrical conductivity (σ) and thermal conductivity (K) of the material, the equation for which is ZT=(S2*σ)/K. For room temperature heating and cooling applications, the average ZT should be greater than approximately 1 in order to make a TE device competitive with alternative conventional technologies; hence the best TE materials can possess higher Seebeck coefficients and electrical conductivities while exhibiting lower thermal conductivities. Much research has been done since the 1990s to find an optimal material system consisting of improved intrinsic thermoelectric properties, which are lacking in most current bulk TE semiconductor materials.
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